Hooks: Expose rollbacks caused by message edits

First of all, thanks for building Codex. It's an awesome app!

What variant of Codex are you using?

App

What feature would you like to see?

When a user edits a message, the conversation is rolled back to that point and all subsequent messages are deleted. UserPromptSubmit doesn't expose any field indicating when this happens.

Some tools use hooks to keep their own copy of the conversation. Right now, if a user edits an earlier message, the hook only sees UserPromptSubmit. That makes the edited message look like a new message added at the end of the conversation.

Additional information

_No response_